1. Via the sales package which is applied every time a payment comes through. This is not typically the way you should apply credits for upgrades.

2. Via the member level. You can specify the credits a member will receive each month through the membership type. The credits will be given out the first time a member logs in each month. Since this NOT based on any payment, all upgraded members will receive the credits and not just paid upgrades. This is useful if, for example, you swap upgrades with another TE owner or give a complimentary upgrade. It also allows credits to be given monthly on yearly upgrades versus only having the credits applied once a month.

It is possible for "double dipping". If you specify credits in the sales package and also in the membership level, a paid upgrade would receive the credits when the payment goes through and also when they log in for the first time each month, so only having credits specified in the membership level will prevent this.

Also, be careful on temporary upgrades. When a member upgrades or perhaps a mod gives them a 1 day upgrade, for example, they receive the credits specified in the membership type which is not what you may want to happen. Instead, create another membership and duplicate the settings for the upgrade except for the credits and use this new membership type for the temporary upgrade. This would especially be true in cases of mods that will allow a member to select a 1 day free upgrade.